This invention generally relates to aircraft roll control systems. Particular application is to aircraft with vortex stabilizing capabilities such as highly swept wings or spanwise blowing device. Roll control is achieved with a leading edge flap system and vortex flow manipulation.
Leading edge flaps are known to the prior art. One such device is the Krueger flap (see e.g., Dommasch D. O., Airplane Aerodynamics, Pitman Publishing Corporation, 4th ed., p. 186). The Kreuger flap pivots about the leading edge of the airfoil to augment lift. By rotating the leading edge flap downward below the chord line, the camber of the wing is increased. This increase in camber increments lift. The Krueger flap, however, is not used for roll control. It functions solely by camber modification rather than vortex generation.
The patent to Kasper (U.S. Pat. No. 3,831,885) discloses another type of leading edge flap. Kasper's flap produces lift on low performance aircraft through vortex generation. It is designed and structured for low performance aircraft. As a result, the flaps are necessarily highly cambered and thicker than the present invention. Also, the length and width of the Kasper flap represents a greater percentage of the associated wing's span because of its low performance wing application. Kasper's flaps are not used for roll control. Spanwise lift distribution over the wing is not manipulated to create a rolling moment. The Kasper flap is used solely to augment lift on low performance tailless aircraft.
The problem of roll control exists with all aircraft. Solutions have been varied and numerous. Generally, ailerons or spoilers provide the rolling moments needed for aircraft maneuverability about their longitudinal axes. These control surfaces, however, are essentially dependent for efficient operation on attached flow over the wing's upper surface. As a result, ailerons and spoilers are largely ineffective when flow separation occurs ahead of them near the leading edges of the wings. The loss of roll controllability with these prior art devices in high lift conditions, when lateral stability and roll damping are also reduced, deteriorates tracking ability, handling characteristics, and resistance to departure from controlled flight. The present invention avoids these adverse effects with the use of independently operated leading edge flaps.
It is therefore an object of the invention to disclose a roll control system that uses a leading edge flap device to create a vortex that shifts the center of lift on one wing panel outboard to produce a controllable rolling moment away from the deployed flap.
A further object of the invention is to provide a roll control device allowing roll moment control at high angles of attack where prior art roll control systems are least effective due to boundary layer flow separation close to the leading edge of the wing.
Another object of the invention is to provide a roll control device, unlike traditional aileron controls, that produces favorable yawing moments in flight that are not adverse to coordinated flight control.
A still further object is to provide a device that when used in combination with conventional elevons produces a synergistic control effect making simultaneous use of the leading edge flap and elevons more effective to control roll than a simple addition of their individual effects would indicate.
A final object of the invention is to provide an alternate mode that is a powerful airbraking system by deploying both leading edge flaps simultaneously to cause rapid and controlled deceleration from high speed flight with neither an increase in pitching moment nor a required trim change.